It's about a girl named Adele who goes to St. Maria's Catholic high school (Co-Ed) however, this bookworm is actually the Queen of Hell in disguise, she goes out a night and kills the lowlife demons who sully the name of their sacred race by preying on humans and becoming true monsters(like...a dark magical girl)
However, there is a little hitch in her master plan, St. Maria's isn't your average high school, this innocent catholic school is actually just a front for a school to train future demon hunters, their goal? Eradicate all demons, of course,
and they've been here long enough to notice one demon appeared at all scenes of demonic activity throughout thousands of years
the demons Queen, Adalay(Ah-dah-lay)-they eventually deduced she was the Queen of Hell, and made their main goal is to kill her.
However, no matter how hard they search, they can never find this Adalay's human form, because who of them would suspect the quiet little bookworm Adele, head of the team in charge of tracking and exterminating demons, the one who endlessly fights those demons, searching for Adalay without pause?